1. Field of the Invention
The present invention relates to wheelchair access systems employing platforms, and more particularly to a wheelchair lift platform structure having stacking platform sections for use in conjunction with a vehicle having a floor from which the system is deployed and stowed to provide an unobstructed view from within the vehicle.
2. Description of the Related Art
Vehicular wheelchair access systems for handicapped persons, such as lifts and ramps, can be mounted on vehicles and made deployable/stowable with respect to the vehicle. Wheelchair users typically move their wheelchair along the lift or ramp platforms in order to transfer from the ground to the vehicle and from the vehicle to the ground using a lift mechanism and platform structure, which may be operated mechanically, electrically, pneumatically or hydraulically, etc. Known wheelchair lift platform structures include solid rigid panels or floors as platform structures that must be stowed away within the vehicle itself. Accordingly, the wheelchair access system is used in conjunction with a portion of the floor space of the vehicle and further may obstruct passageways and restrict the amount of available space within the vehicle.
For handicapped persons, mobility is enhanced with the availability of wheelchair access systems that are powered to provide much or all of the movement of the motorized platform structure. This is particularly useful due to the inconvenience of physical activity by the wheelchair passenger. Such lifts typically have pivotal mechanisms for raising and lowering platform structures, see e.g., U.S. Pat. No. 5,261,779 to Goodrich for “Dual Hydraulic, Parallelogram Arm Wheelchair Lift” issued 16 Nov. 1993 and U.S. Pat. No. 6,238,169 to Depuy, et al. for “Dual Function Inboard Barrier/Bridge Plate Assembly for a Wheelchair Lift” issued 29 May 2001 to applicant's assignee. Each of these disclose dual hydraulic, parallelogram arm wheelchair lift assemblies for use typically in commercial vehicles. The lift assembly has a platform connected to a parallelogram linkage. In both of the above assemblies, when the platform of the lift is in a stowed position, the platform essentially blocks the doorway, making it very inconvenient to use the doorway or the windows on the vehicle door. Moreover, the wheelchair access system being fixed on the floor of the vehicle itself may provide limited space and visibility from and within the vehicle.
Other wheelchair lifts that do not completely block the door when in a stored position have been described, e.g., U.S. Pat. No. 4,664,584 to Braun, et al. for “Rotary Wheelchair Lift” issued 12 May 1987 discloses a rotary hydraulic lift having a vertically-telescoping slide tube and a horizontal wheelchair platform support arm attached to the lower end of the slide tube allowing the platform into or out of the vehicle parallel to the slide tube. However, the platform structure and pivotal mechanism employed in rotatable wheelchair lifts require a substantial amount of space.
Devices known in the prior art have only been partially successful in providing safety, stability and ease of operation in regard to the design of the lift and platform structure. Foldable and multiple section platform assemblies are known to decrease the platform area when not in use. Known examples of platform structures employing hinges between inner and outer platform sections such that the outer section rises and folds against the inner section on the outer side include U.S. Pat. No. 6,379,102 to Kameda for “Wheelchair Lift with Foldable Platform” issued 30 Apr. 2002. A lack of predictability of operation while being folded or unfolded, however, is a substantial disadvantage associated with this type of platform assembly when the platform structure is deployed from its stowed position. For example, in the stowed position the outer platform section, unless properly hooked, can dangle and assume a variety of positions. Roll-stops to prevent the wheelchair passenger or operator from interaction with the lift structural componentry have either not been provided or are not effective. Additionally, exposed rigid linkages may come in contact with the operator or passenger. Such linkages, in addition to being unsightly and annoying, may also present a substantial safety hazard to passengers and operators who come into with them during the operation of the lift. Moreover, cable systems have a number of other drawbacks, among them being that the cable is difficult to adjust properly and requires frequent readjustments as the cable stretches and tends to lengthen or shorten with temperature. In addition, a cable can fray or break in use and has limited strength. Many previously known lift devices also have a tendency to sway, rotate, jump or bind as the lift is operated, which provides additional potential risk.
To address the growing concern for passengers who are handicapped or otherwise have limited mobility, it would be desirable to provide compact, storable wheelchair access systems that minimize the space they occupy on the floor of the vehicle for storing the lift platform structure while providing for enhanced access to the door and particularly the door window for unobstructed views from within the vehicle.